Gas sink in the form of an interstitial flushing device

ABSTRACT

The invention concerns a gas-porous plug in the form of an interstitial flushing device in which the gas passage ducts are in the form of interstices. The opposite walls of the interstices are monolithically interconnected by flat bridges of refractory material. The gas-porous plug can be produced by means of a conical hollow body (1) whose side wall (2) comprises apertures (3). The hollow body (1) is inserted into a casting mould (4) which is subsequently filled with a refractory casting compound.

BACKGROUND OF THE INVENTION

The invention relates to a gas-porous plug for metallurgical vesselscomprising a refractory moulding in which at least one gas passage ductis provided in the form of an interstice running through the plug from acold side of the plug to a hot side thereof.

Gas-porous plugs of this type are referred to as so-called interstitialflushing devices and function to blow reaction or purification gasesinto molten metal or metal melts.

In the latter context, such gas-porous plugs are usually used in thebase area of a refractory lining of a metallurgical vessel, particularlya steel ladle, and such metallurgical vessels are pressurized withcompressed gas through a gas feed pipe.

Conventional gas-porous plugs are known which are constituted as aninner conically shaped refractory moulding or body over which a secondouter conically shaped moulding is positioned. In order to define a gapbetween the inner and outer mouldings, strip-shaped spacers are insertedin the gap or interstices therebetween. Thus, such gas-porous plugs arenot monolithic structures.

A peripheral side wall and a base area of such conventional gas porousplugs are also usually provided with a gas-tight, welded sheet metalcasing having a base positioned at a distance from the underside or coldside of the gas-porous plug to create a gas feed chamber. A gas feedpipe is welded to the metal base and opens into the latter gas feedchamber.

In another conventional gas-porous plug, the interstice is formedbetween the side of the sheet metal casing and the refractory moulding.However, such gas-porous plugs are no longer used owing to theirrelatively low wear resistance.

Another gas-porous plug of a conventional construction is disclosed inDE-OS 43 12 988 in which gas passage ducts are defined as athree-dimensional network in the interior of a monolithically castrefractory moulding utilizing a conventional tensioning device. However,the manufacture of this gas-porous plug is relatively complicated andthe inner gas passage ducts are also relatively long which results incomparative high pressure gas losses when in use.

In another conventional gas-porous plug disclosed in DE-OS 38 23 897,threads or strips are inserted into a casting mould utilizing atensioning device which is pulled or burnt out after the moulding hasset. This moulding is also manufactured as a monolithic structure butthe tensioning of the individual threads constitutes a relativelycomplicated manufacturing process.

SUMMARY OF THE INVENTION

This invention is directed to a novel gas-porous plug and themanufacture thereof in a relatively simplified fashion. The gas-porousplug of the present invention is defined by an inner body which issurrounded by an outer body with a peripheral gap therebetween. Theperipheral gap is spanned by a plurality of bridges. The inner and outerbodies and the plurality of bridges are formed as a single piece ofmonolithic cast refractory material.

Preferably, the gas-porous plug is manufactured by placing an openhollow body in the form of a generally conical sleeve having aperturesin a side wall thereof into a casting mould with an exterior surface ofthe sleeve spaced from an interior surface of the casting mould. Thishollow body or sleeve is made from material that can be burnt or meltedout. The casting mould is then filled with refractory casting compoundwhich fills the sleeve-like body, the openings thereof and a peripheralgap between the exterior of the sleeve and the interior of the mouldsurface. The sleeve is then burnt or melted out, and the gas-porous plugremains and is defined by a single piece of monolithic cast refractorymaterial formed of an inner body, an outer body and a plurality ofbridges therebetween.

The gas-porous plug thus constructed in accordance with this inventiondisplays directed porosity and possesses characteristics of both aninterstitial flushing device and a gas-porous plug with individual gaspassage ducts. In contrast to conventional interstitial flushingdevices, the refractory material bridges span the gap or intersticebetween the inner and outer bodies and thus monolithically connect thesame to each other. Owing to this monolithic construction, thegas-porous plug displays excellent durability and the volume of the gaswhich is injected into the molten metal or melt can be preciselyregulated in a relatively simple manner by varying, for ample, thethickness of the peripheral gap or interstices or the size and number ofbridges spanning the same as a function of the operating pressure of theflushing gas.

Additionally, the bridges spanning the peripheral gap or intersticecreate eddies in the gas as it flows through the gas-porous plug. Suchgas eddies result in the gas leaving the hot side of the gas-porous plugin a highly desired turbulent flow which allows fine distributionthereof inside the metal melt. The latter not only improves the flushingeffect of the gas thus injected into the molten metal, butsimultaneously this also prevents excessive flow velocities occurring onthe hot side of the plug which would otherwise result in increase wearof the gas-porous plug.

In order to increase the volume of the injected gas, a plurality ofinterstices can be provided, preferably ending in concentric circles orsemi-circles on the hot side of the flushing device. An optical wearindicator can also be readily provided the gas-porous plug to reflectin-use wear, particularly at a lower end area of the gas-porous plug.Once the gas-porous plug is worn down in the lower area, a dark innerarea will be visible, thus providing an optical indication of the wearstatus of the plug. Gas-porous plugs with such optical wear indicatorsare known, for example, from European Patent Application 0 325 709.

The open hollow body or sleeve having the apertures therein ispreferably made of plastic to allow it to be melted or burnt out of thecast refractory material gas-porous plug. Preferably, this aperturedsleeve is of a conical configuration having a narrower end which ispreferably placed on the bottom of the associated casting mould. Thisallows the mould and the sleeve to be readily filled from the top. Thenarrower bottom end of the eventually cast gas-porous plug constitutesthe hot side thereof, whereas the larger upper end is the cold sidethereof. Preferably, the apertured plastic sleeve is burnt or melted outafter the refractory material cast in the mould has set or during itsdrying, and this leaves behind the generally peripheral gap spanned bythe bridges which additionally monolithically unite the inner and outerbodies which are respectively preferably substantially conical andconically sleeve-like.

If desired the wear resistance of the gas-porous plugs can be increasedby incorporated carbon carriers into the refractory casting materialprior to the casting operation earlier described.

With the above and other objects in view that will hereinafter appear,the nature of the invention will be more clearly understood by referenceto the following detailed description, the appended claims and theseveral views illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a schematic front view of a mould and an apertured sleeveinserted in the mould prior to the performance of a casting operation toform a gas-porous plug.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A conical hollow body or sleeve 1 is illustrated inserted substantiallycentrally in a likewise conical casting mould 4 with substantial equalcircumferential/peripheral spacing therebetween. The conical hollow bodyor sleeve 1 includes an opening at the top and a side wall 2 thereofincludes a plurality of substantially circular apertures or openings 3.

The casting mould 4 is filled with free flowing refractory compoundmaterial which fills the gap between the sleeve 2 and the inner surfaceof the mould 4, the interior of the sleeve 2 and the openings orapertures 3 therein. Since the casting compound or material flows intoand fills the apertures 3 during pouring, corresponding bridges areformed in the apertures 3 spanning and eventually uniting whateventually becomes the exterior hollow sleeve-like outer body of thegas-porous plug and the conical interior body thereof. After filling therefractory casting compound in the mould 4, the latter can be vibratedand the material otherwise compacted, as is customary and conventional.

After the refractory material has set or during its drying, the plasticsleeve 2 can be burnt or melted out resulting in the as-porous plugessentially being defined as a one-piece monolithic cast refractorymember formed by a conical inner body, a conical sleeve-like outer body,and a plurality of bridges therebetween.

Although a preferred embodiment of the invention has been specificallyillustrated and described herein, it is to be understood that minorvariations may be made in the apparatus without departing from thespirit and scope of the invention, as defined the appended claims.

I claim:
 1. A gas-porous plug for metallurgical vessels comprising aninner body surrounded by an outer body with a peripheral gaptherebetween, said peripheral gap being spanned by a plurality ofbridges, and said inner and outer bodies and said plurality of bridgesbeing a single piece of monolithic refractory material.
 2. The gasporous plug as defined in claim 1 wherein said inner body is of asubstantially conical configuration.
 3. The gas porous plug as definedin claim 1 wherein said outer body is of a substantially conicalconfiguration.
 4. The gas porous plug as defined in claim 1 wherein saidinner and outer bodies are each of a substantially conicalconfiguration.
 5. The gas porous plug as defined in claim 1 wherein saidouter body is substantially a sleeve.
 6. The gas porous plug as definedin claim 1 wherein said outer body is substantially a conical sleeve. 7.The gas porous plug as defined in claim 1 wherein said refractorymaterial is cast material.
 8. The gas porous plug as defined in claim 2wherein said outer body is substantially a sleeve.
 9. The gas porousplug as defined in claim 2 wherein said outer body is substantially aconical sleeve.
 10. The gas porous plug as defined in claim 2 whereinsaid refractory material is cast material.
 11. The gas porous plug asdefined in claim 4 wherein said outer body is substantially a sleeve.12. The gas porous plug as defined in claim 4 wherein said outer body issubstantially a conical sleeve.
 13. The gas porous plug as defined inclaim 4 wherein said refractory material is cast material.
 14. A methodof manufacturing a gas-porous plug comprising the steps of:(a) providinga sleeve having a plurality of aperture extending transverselytherethrough, (b) inserting the sleeve in a mould having an interiormoulding surface spaced from an exterior surface of said sleeve, (c)casting a refractory casting compound interiorly and exteriorly of saidsleeve and in said apertures, and (d) burning or melting out the sleeveto thereby form the gas-porous plug as a one-piece monolithic castingdefined by substantially spaced inner and outer bodies joined by aplurality of bridges therebetween.
 15. The gas-porous plug manufacturingmethod as defined in claim 14 wherein the sleeve has an exterior conicalsurface and the interior molding surface is conical whereby the outerbody is a conical sleeve.
 16. The method of manufacturing a gas-porousplug as defined in claim 14 wherein the inner body is substantially of aconical configuration.
 17. The method of manufacturing a gas-porous plugas defined in claim 15 wherein the inner body is substantially of aconical configuration.